How do I restore my iPhone 6s+

Restore?

Restore to factory settings = Restore your iPhone, iPad, or iPod to factory settings - Apple Support

Restore from backup = Restore your iPhone, iPad, or iPod touch from a backup

If you meant something different, please explain.

Regards

Giulio

See this, Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

If you wish to restore to factory, see this, Restore your iPhone, iPad, or iPod to factory settings - Apple Support

I suspect we're keeping company tonight :-)

Take care, my friend.

Giulio

Yes we are. And the same to you.